Enhanced understanding of the natural history and mechanisms of the brain's response to stroke will facilitate the development and testing of novel approaches to the rehabilitation of stroke survivors. The goal of this project is to use advanced neuroimaging techniques to investigate the cortical changes that follow ischemic stroke, and to correlate these observations with cortical motor maps obtained with transcranial magnetic stimulation and with clinical outcome. The project will identify a variety of patterns of brain reorganization and determine which ones are common to patients with good recovery of motor function. These data, in combination with those from Dr. Pons' project, will allow identification of patterns and mechanisms of plasticity which appear to be beneficial. This may facilitate the development of novel pharmacological or behavioral interventions targeted to enhancing these mechanisms in an effort to improve the eventual functional recovery of stroke survivors. Understanding these patterns may also allow individualized selection of recovery-enhancing therapies in patients recovering from stroke, potentially decreasing both the cost of rehabilitation and the substantial burden of disability and decreased quality of life caused by this disease. We propose to use functional Magnetic Resonance (fMRI) techniques to measure cerebral activation during a variety of tasks in patients at three times during the recovery from stroke. The tasks will include simple movements of the affected hand which can easily be correlated with magnetic stimulation maps and with others' previous imaging studies of recovery from stroke, contralateral and bilateral hand movements to examine the importance of interhemispheric inhibition and mirror movements in the activation. The independent prognostic value of routinely obtained MR maps of cerebral perfusion and diffusion will also be examined. These data will also facilitate the reconciliation of the blood oxygenation- based MR data with the magnetic stimulation data, which is based upon electrical stimulation of cortical pyramidal tract cells.